Drain and rinse the tofu. Pat it dry very well with kitchen paper towels. Add it to a high-speed blender. Drain and rinse the young jackfruit, remove the hardcore parts and discard. Add the jackfruit to the blender. Note: after removing the hardcore parts of the jackfruit, you should end up with about 7 ounces (200g) of jackfruit.
Add the water, oil, salt, and onion powder to the blender and blend on high speed for about 30 seconds, or until very smooth.
Transfer the wet mixture to the bowl of a stand mixer fitted with the flat beater/paddle. Add the vital wheat gluten and all-purpose flour. Knead on speed 2 for about 5 minutes.
At first it will look very wet, that is normal. Keep kneading. Once it's starting to turn into a dough, replace the flat beater with the dough hook and keep kneading on speed 2 for at least 20 minutes. This may seem like a long time but it's essential to get a very fibrous texture. Make sure you stay near the stand mixer as it will probably move. The dough will be soft and slightly sticky. Again, this is normal, you don't want the dough to be too firm.
Once the dough has a fibrous texture, divide it into two balls. Shape each balls into a log and wrap tightly in aluminum foil. Wrap in a second layer of foil.
Fill a pressure cooker (or Instant Pot) with cold water to the 2/3 (about 3 liters). Place the seitan logs in the pressure cooker. The logs will be submerged in water.
If using a pressure cooker: heat over medium heat, once it is under pressure, cook for 30 minutes. If using an Instant Pot: set to Manual Pressure Cook and set the time to 30 minutes.
After 30 minutes, release the pressure. Carefully remove the seitan rolls from the cooker and let them cool completely.
Once cold, remove the rolls from the aluminum foil, transfer to a plate and cover with plastic film. Refrigerate for at least 4 hours. I found out that chilling in the refrigerator for a few hours gives it a more fibrous, meatier texture.
Next, using your hands, shred/pull the seitan chicken into bite-size pieces (or larger pieces!). You can now use it in any recipe! I recommend preparing a marinade before stir-frying or baking to add more flavor.
Chick'n will keep in the refrigerator for up to 3 days.